1. Field of the Invention
The present invention relates to a photoelectric conversion device having a dual damascene structure and a method for making the photoelectric conversion device.
2. Description of the Related Art
Recently, high image quality, reasonably priced digital cameras and video cameras are gaining popularity. These image-input appliances are equipped with charge-coupled device (CCD)-type or metal oxide semiconductor (MOS)-type photoelectric conversion devices. A MOS photoelectric conversion device is constituted by a photoelectric conversion element, a MOS transistor, and other associated components. A MOS transistor can be formed by a complementary MOS (CMOS) process for general semiconductors.
A MOS-type photoelectric conversion device uses a multilayer interconnection structure. Japanese Patent Laid-Open No. 2004-221527 discloses use of copper as a wiring material to decrease the thickness of the wiring and thereby decrease the height of a photoelectric conversion device having a multilayer interconnection structure.
Japanese Patent Laid-Open No. 2002-368203 discloses a shared contact that connects the gate electrode of a MOS transistor to a floating diffusion region in a last-stage amplifier of a CCD-type photoelectric conversion device.
In a photoelectric conversion device, the aperture through which light is incident on a photoelectric conversion element is defined by wiring. Accordingly, in order to increase the light collecting efficiency and improve sensitivity, a wiring layout with a wide aperture allowing light to enter the photoelectric conversion element is desirable. Moreover, since a MOS-type photoelectric conversion device requires a larger number of wiring layers than a CCD-type photoelectric conversion device, the flexibility of designing the wiring layout is low. Thus, when the pixels are miniaturized, the design flexibility of the wiring layout of the MOS-type photoelectric conversion device is further degraded.
Even when the aperture is made wide, it is difficult for oblique light to enter the photoelectric conversion element if the distance between the photoelectric conversion element and the aperture is large. The thicker the insulating film is on the photoelectric conversion element, the larger the amount of light absorbed by the insulating film. This decreases the light collecting efficiency on the photoelectric conversion element.